~5 week old chick not as active

So, yesterday I think my toddler stepped on or perhaps squeezed one of the 5 weeks old chicks. She seemed a bit shocked at first, but alot better yesterday night. However, I noticed she wasn't participating into tonight's mealworm frenzy.

She doesn't seem sick so much as possibly in pain? When I picked her she sounded like she was making a clicking sound. I have seen her open her wings, though not so vigorously as to try and fly away. Previously, she would have probably tried, but not very much at all today. Anyway, I've taken her inside and I got her to eat two mealworms. As a runt, she is used to running away with her food. She tried to do that tonight and I noticed she looked like she might be hurt. She was just moving alot slower and tried to go climb over the feed bowl, but instead sort of stumbled over it. She still ate in though, so I guess that is good. She was sleeping standing up for a little bit and now is laying down. I gave her a little look over, but can't pinpoint anything as to what exactly is the cause.

Is there anything I can give the chick to make her odds better? Also, any ideas of something I could look for as to the cause (injury) or is the bird sick? Anyone who has had this happen in the past?

Well, she went downhill quickly, breathing is heavier and she was a bit floopy last I checked on her. She was standing and sleeping earlier and had yellow poo. I'm starting to wonder if it even was my toddler.. Do you think it could be coccidiosis?

I asked hubby to grab some corid and probiotic from the feed store. Not keeping my hopes up, but should I go ahead and treat the rest of the flock too? Any chance for the chick?

Corid won't hurt them even if they don't have it, but I would start it. When you get the Corid, dosage is 2 tsp of the liquid or 1 1/2 tsp of the powder per gallon of water. Give the chick a couple of drops of the undiluted Corid liquid (or mix 1 1/2 tsp of the powder in 2 tsp of the water, and give a couple of drops of that.) In the morning, repeat that, and make sure the chick is drinking. Look for any not eating or standing around hunched. I hope that she survives.

Got the corid started for everyone. She is barely hanging on though. How do I get her to drink? I have a syringe dropper, but I can't get her to open up and she doesn't have waddles yet. Poor gal, she was my favorite

Just got her to drink a bit with the help of hubs prying her beak open. Hopefully she will perk up a bit. Should we repeat in 2 hours before bed?all other chicks are good.Do the stores normally already have the chicks vaccinated or do we need to do that? A whole side to owning chickens I didn't think about lol.

It would probably be too late to vaccinate for cocci, especially if they have been exposed. I don't know if the vaccine is even for sale or easy to find. Give some more in the morning. But she still need still need the fluids.